Fisher 656 Instruction Manual

Instruction Manual
Form 5504
September 1998
Type 656 Diaphragm Actuators
Fisher Controls Type 656 actuators are long stroke,
spring opposed, direct-acting diaphragm actuators.
They operate Vee-Ball valves, butterfly valves, built-
in turbine valves, louvers, dampers and similar equip-
ment. They are suitable for either push-down-to-close
(PDTC) or push-down-to-open (PDTO) applications
and are available in sizes 30, 40 and 60 to provide
2-1/8", 3-1/2" and 4-1/8" travel, respectively.
In a direct acting diaphragm actuator, increasing load-
ing pressure moves the actuator stem downward,
compressing the spring. When the diaphragm pres-
sure is decreased, the spring moves the actuator stem
upward. In the event of failure of the loading pressure
or the operating medium pressure to the controller, the
actuator stem moves to the extreme upward position.
When an actuator and valve are shipped together, the
actuator is normally mounted on the valve. Follow the
valve instructions when installing the valve and actua-
tor in a pipeline. If the actuator is shipped separately,
or if it is necessary to mount the actuator on the valve,
four holes have been tapped into the yoke boss to an-
chor it to a mounting bracket.
WARNING
To avoid personal injury or property
damage caused by bursting of pressure
retaining parts, be certain the dia-
phragm casing pressure does not
W0454 / IL
Figure 1. Type 656
exceed the limits listed in the Specifica-
tions table. Use pressure relieving or
pressure limiting devices to prevent the
diaphragm casing pressure from ex-
ceeding these limits.
To make the stem connection, follow the appropriate
assembly step 10 in the Maintenance section. Stan-
dard actuator sizes 30 and 40 have mounting holes
tapped 3/8" UNC, and the size 60 mounting holes are
tapped 1/2" UNC.
Type 656